© Reuters
Rebels in eastern Libya have mobilised to stop the advance of pro-Gaddafi forces

Every move in the diplomatic play-book has so far been thrown at the embattled Libyan leader Muammar Gaddafi and yet he is still hanging on to power.

Assets have been frozen, an arms embargo applied, and legal proceedings are being investigated by the International Criminal Court.

There's even been talk of an internationally enforced no-fly zone to prevent the Libyan leader using his air force to attack his own people.

Nobody, of course, believed that the machinery of international condemnation alone would topple the Libyan leader. That looked as though it was well in hand by Libyan opponents of his regime.

But as the fighting around Brega underscores, neither side seems to have the knock-out punch capable of defeating the other. Col Gaddafi appears unable to re-capture the eastern part of his country. And for now, his opponents seem unable to mount a major offensive against Tripoli.

Painted into a corner

Even defence experts are uncertain about how to weigh the capacities of the pro- and anti-Gaddafi forces. The situation is seen as "extremely fluid". The pro-Gaddafi forces are seen as having largely finite resources, though this may depend upon access to funds, while his opponents are only now beginning to organise and train. The next few weeks will be crucial.

A stalemate on the ground in Libya could be a serious problem for international diplomacy. The humanitarian and refugee problems will continue - indeed, they could get worse. And nobody knows what impact events in Libya will have upon the dynamics of instability elsewhere in the region.

There's a strong sense that many foreign governments believed that Col Gaddafi was on the way out and that his fate was sealed. The diplomatic measures against him were intended to hasten his departure and to express support for the Libyan people's aspiration for freedom.

There's a danger that, having been painted into a corner, Col Gaddafi may well have little option but to cling on to power for as long as he can.
No-fly zone option

All of the talk about possible outside military options has to be seen in this light. The talk of no-fly zones and the movement of US warships through the Suez Canal into the Mediterranean is for now largely political in intent: an additional set of signals to Tripoli that the international community means business.

However, as fast as British Prime Minister David Cameron has invoked the idea of a no-fly zone, key figures in the Obama administration have sought to play down the option - chief among them US Defence Secretary Robert Gates.

Indeed, a speech by Mr Gates to the US Military Academy at West Point last week seemed to rule out any major US military activity in Libya. He noted that "any future US defence secretary who advised the President to again send a big American land army into Asia or the Middle East should have his head examined".

The problems are not so much military as again political. The US and its Nato allies could clearly enforce some kind of air exclusion or no-fly zone as they have done in the past over Serbia and Iraq. But this would inevitably entail the use of lethal military force. It would be a small but significant step towards full-blown intervention.

Colonial past

The Middle East is a tinder-box at the moment with smouldering embers threatening to erupt into full-scale conflagrations in several countries.

Whatever an outside military role might mean in Libya itself, and there's lots of bad history here - due not least to the colonial past and Washington's bombing of Tripoli in April 1986 - it would inevitably have wider ramifications throughout the region.

Many of the military assets being deployed at the moment could play a useful role in helping to alleviate the humanitarian crisis on Libya's borders. Could there still be an external military option? Of course there could.

Supposing a Libyan government warplane bombed a school or refugee camp, killing large numbers of civilians, and the reports were relayed around the world on satellite TV?

That could change the calculations in Washington and European capitals. But for now, the watchword is caution.